Cooling ducts for wound coils



C. L. MOORE Filed May 29, 1963 INVENTOR Curtis L. Moore ATTORNEY FigB 88 2Q Fig.8A

M 9o a 4 Y pw@ C B C 6 6 3 ..4 F

COOLING DUCTS FOR WOUND COILS CL22 24D July 13, 1965 Figfr. ge

9s 94 5o e lai 4 United States Patent O 3,195,085 CGLING DUCTS FOR WUND QUELS Curtis L. Moore, Hickory Township, Mercer County, Ila.,

assigner to Westinghouse Electric Corporation, Pittsburgh, Pa., a corporation oi' Pennsyivania Fiied May 29, 1963, Ser. No. 284,232 7 Claims. (Cl. 336-66) This invention relates in general to electrical transformers and cooling ducts therefor, and more particularly to cooling ducts incorporated in foil or sheet wound transformers.

It is well known that heat is produced in laminar core or coils used in electrical transformers when the transformers are energized. The heat produced in a transformer coil is chielly a result of the 12R loss of the energized winding. The heat produced in an energized transformer core is in a great measure due to eddy currents and hysteresis losses. It is desirable to conduct this heat away from the transformer core and coils to prevent excessive temperature rise. In foil wound electrical coils, axial ducts have the disadvantage of requiring the heat from remote areas of the coils to be passed through several layers of turn-to-turn insulation to reach the ducts. Radial ducts in foil wound coils present an insulation creepage problem across the face of the duct similar to those experienced across the face of the coil. Creepage is the phenomenon of electrical conduction or discharge between conductors which are separated by insulation.

Accordingly, it is a general object of this invention to provide a new and improved cooling means for electrical inductive apparatus.

It is a more particular object of this invention to provide a new and improved cooling means for foil or sheet wound transformer coils.

It is yet another object of this invention to provide a new and improved cooling means for wound magnetic cores.

Other objects of this invention will in part be obvious and will in part appear hereinafter.

Briely, the present invention accomplishes the above cited objects by providing holes in the turns of the core or layers of the coil to be cooled. When the core or coil is assembled, the holes are placed in staggered juxtaposition so as to produce diagonal ducts through the element to be cooled. More specifically, the holes are staggered to produce ducts which are of greater length than if 4the holes were placed in perfect juxtaposition. This staggering of adjacent holes Ialso increases the creepage distance which must be traversed by any electrical discharge between adjacent layers of the device being cooled.

Further objects and advantages of the invention will become apparent as the following description proceeds and features of novelty which characterize the linvention will be pointed out in particularity in the claims annexed to and forming a part of this specification.

For a better understanding of the invention, reference may be had to the accompanying drawings, in which:

FIGURE l is a top plan View of a spirally wound cylindrical coil embodying the teachings of the invention;

FIG. 2 is a vertical transverse sectional view of the cylindrical coil of FIG. l taken along the plane H II;

FIG. 3 is a series of partial sectional views taken at successive planes through a portion of FIG. 2;

FIG. 4 is a top plan view of another cylindrical wound coil embodying the teachings of the invention;

FIG. 5 is a vertical transverse sectional view of the cylindrical wound coil of FIG. 4 taken along the plane V-V;

lSS Patented July 13, 1965 FIG. 6 is a series of partial sectional Views taken at successive sections through a portion of FIG. 5;

FIG. 7 is a stacked laminated magnetic core embodying the teachings of the invention; and

FIGS. SA and 8B show two enlarged partial sectional views of wound structures having transverse cooling ducts.

Referring to FIG. l of the drawings, there is shown a top plan view of a wound coil structure 82 embodying the teachings of the invention. A plurality of ducts such as ducts l@ and 12 are shown radiating from the interior of the structure. Each duct is in contact with all layers of the coil structure 82 to insure eicient cooling. While eight ducts are shown, it will be understood that as many ducts as needed may be used to carry away the heat generated in the coil structure 82. A tube 14 may be provided in contact with the inside of the coil structure. Tube 14 may be made of electrical insulation; one purpose of tube 14 is to provide a mandrel about which the coil structure is wound. Tube 14 also serves as an inner stop to the ducts such as duct I2, as best seen in FIG. 2. The structure may be immersed in a cooling fluid such as transformer oil.

The ducts are produced by rst making a series of holes in a strip of electrical conductor which is coated on at least one side with electrical insulation. The holes are so spaced that when the strip is wound into a coil successive holes along the long dimension of the strip are superimposed. When the coil is wound the holes are axially offset from one another to increase the -average creepage distance between turns as may be best seen from FIG. 8B.

In FIG. 2 ot the drawings, there is shown a vertical transverse sectional view of the cylindrical layer wound structure of FIG. l taken at section II-II. In this view, one may see how the ducts 10 and 12 are arranged so as to achieve a long multi-directional or zig-zag coolant path through the structure that is to be cooled. For example, if the structure shown is a sheet wound transformer coil, each duct will pass through each turn of the coil twice. To illustrate, the duct 12 enters the structure at the lower right-hand corner of the coil and passes upward and inward to the tube i4. The duct 12 then makes an approximate turn and proceeds downward and outward t0 a point near the lower left-hand corner of Ithe structure. The direction of the arrows D and E represents one Way in which a cooling tluid may flow through the coil either as a result of natural convection or due to pumping of the coolant. It will be observed that the length of the path of fluid ilow or travel through the duct 12 is arranged to be greater than the lineal distance between the linside and outside of the structure to increase the creepage distance between turns, to increase the cooling surface, and to increase the creepage distance between the inside and outside of the structure. The walls of the ducts 10 and 12 appear smooth because of the scale of FIG. 2; the ducts are actually stepped as best seen in the enlarged View of FIG. 8B. If the ducts were formed by drilling after the coil was wound the walls would indeed be smooth and the creepage distance between adjacent turns would be limited to the thickness of insulation between turns. In the ducts of my invention, the average creepage distance between adjacent turns is increased by making the holes before the coil is wound and then winding the coil to place the holes in staggered juxtaposition to form ducts which are longer than the radial thickness of the coil.

In FIG. 3 of the drawings is illustrated a number of partial views taken through a portion of the laminated cylindrical structure of FIG. 2. The views 3A, 3B and 3C are taken along the planes IIIA-IIIA, HIB-HIB, and IIICIIIC of FIG. 2 respectively. It will be observed that each gure of the structure except FIG. 3A contains two holes; FIG. 3A contains but one hole 16. The holes enanos-e 22 and 24 of FIG. 3C, are spaced further apart than the holes )i8 and 2t) of FIG. 3B. This increase in hole spacing gives the duct formed by the superposition of a plurality of such holes a change of direction at the inside of the structure as best illustrated by FIG. 2. The holes, such as hole l of FIG. 3A may be punched while the turns are being wound on a temporary mandrel. lf the turns are coated with electrical insulation, it may be desirable to etch back the metal about the holes to further increase the creepage path before the turns are wound up. This hole etching process may be completed while the edges S2 of ythe turns are being etched. It will be understood that while the method of punching the turns of a laminated structure illustrated produces one bidirectional duct in the structure, the sequence of hole punching may be repeated to produce any desired number of bi-directional ducts in the structure. Although circular holes are shown, any desired hole shape may be used.

Referring to FIG. 4 of the invention, there is illustrated an end View of a wound core or coil employing the teachings of the invention. A centraltube 3i? may be used to direct the flow of a coolant through cooling ducts such as ducts 26 and 28. The coolant flow as shown `by the arrows E and F is from the annular space 32 to the outside of the coil or core structure. The direction of coolant `flow may be reversed if desired for a particular application.

` ln FIG. 5, there is illustrated a vertical transverse sectional view of FIG. 4 taken at section V-V. From this View, it may be seen how a plurality of single direction ducts 26, 27, 28, and 29 are produced through a laminated core or coil assembly by means of staggered holes in adjacent laminations. The coolant flow through the structure may be in the directions indicated by the arrows G, H, I and l or in other directions and may be due to either natural convection or forced coolant flow. It 'is to be understood that the structures embodying the present invention are not limited to a circular shape, but may be of elliptical or other configurations. The walls of the ducts are not smooth but are stepped as described with reference to the ducts of FIG. 2.

At FIG. 6 are illustrated views 6A, 6B and dC, taken along planes VIA-VIA, VfB-VIE, and VIC-VK,` of FIG. 5 respectively. These views illustrate how the holes such as holes 34 and 35 of FIG. 6A. may be shifted laterally in unison in successive turns from the innermost to the outermost layer of the structure. Holes 38 and 40 of FIG. 6B are spaced the same distance apart as are holes 34 and 36 of FIG, 6A but are located closer to the edge 34 of the lamination S6. Similarly, holes 42 and 44 of FIG. 6C are shifted even more toward the edge 3S of lamination 9d. It will be understood that holes may be punched wherever in the structure it is desired to provide a cooling duct.

At FIG. 7 there is illustrated an end elevation of a rectangular laminated stacked magnetic core structure 92 illustrating how the teachings of the invention may be applied to a stacked magnetic core. The laminated core structure 92 comprises 4 stacks of laminations do, 48, Sil and 52. Two ducts 62 and ed are formed in lamination stack 48 by making two holes in each lamination in such positions that after the laminations are stacked the holes are in staggered juxtaposition. By staggered juxtaposition of holes it will be understood that the holes are placed in mutual communication but that the axes of a series of holes in mutual communication are incrementally shifted in successive laminations. In like manner, two ducts 58 and 60 are produced in lamination stack 52.

A lai-directional duct S6 is produced in lamination stack 50 by starting with two spaced apart holes 96 and 98 in one lamination and then in each successive lamination producing two holesV of closer spacing until the two holes merge into one hole 94. Similarly a bi-directional duct 54 is built into lamination stack 46. lt will be understood that while circular holes of uniform size are illustrated, holes of other configurations and of varying sizes may also be used to produce the ducts. The punchings which comprise the core 92 may be stamped with the duct forming holes such as hole 94 in the same operation which produces the laminations. The holes are shifted enough in adjacent laminations to produce a diagonal path for maximum cooling but not enough to prevent the flow of a cooling Huid through successive laminations.

ln FlGS. 8A and 8B there is shown how the holes in successive laminations of a core or successive turns of a foil or sheet wound coil may be placed in staggered juxtaposition so that the average creepage distance required to prevent short circuits between adjacent turns or laminations is maximized.

ln FIG. 8A is illustrated the structure which would exist if the holes which form duct 66 were not staggered. The creepage distance for an electrical short circuit in this case would be only the thickness of the electrical insulation 68 as between adjacent turns or laminations 7d and 72.

ln FiG. 8B where kthe holes in successive turns or laminations which form the duct 'i4 are placed in staggered juxtaposition, Vit will be observed that the maximum creepage distance for an electrical short circuit between adjacent turns or laminations is now the insulation thickness 76 as between turns or laminations 78 and Si) plus the distance each hole is shifted axially from the adjacent hole. This increased creepage distance X lessens the possibility of electrical short circuits between adjacent turns or laminations due to the holes which form the duct 7d. In addition, the length of the duct 74 is increased by the staggering of the holes thereby providing increased cooling in the coreor coil.

lt will, therefore, be apparent that there has been disclosed a duct forming means for laminar heat generating structures of generalV application, but particularly adapted to the cooling of transformer core or coils. When the invention is applied to a foil or sheet wound transformer coil, the need foraxial ducts is eliminated and a solid winding may be produced which has great mechanical strength to resist short circuit forces.

Since numerous changes may be made in the abovedescribed apparatus and different embodiments may be made withoutV departing from the spirit thereof, it is intended that all the matter contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

l claim as my invention:

l. A winding for electric inductive apparatus, including at least one sheet conductor having electrical insulation adjacent to at least one side of said sheet conductor, said sheet conductor having a plurality of holes so spaced that when said sheet conductor is wound into a coil the holes in said sheet conductor are placed in staggered juxtaposition to form at least one duct through said winding.

2. A winding Vfor electrical inductive apparatus, including at least one sheet conductor, said conductor being coated with electrical insulation on atleast one side, said conductor'having a plurality of holes so spaced that when said conductor is wound into a coil the holes in said conductor are placed in staggered juxtaposition to form at least one duct through said winding.

3. A wound core for electrical inductive apparatus which produces heat in normal operation, saidtwoundy core including at least one sheet of ferromagnetic material wound into a plurality of layers, said layers of ferromagnetic material having a plurality of holes so juxtaposed as to form cooling ducts between the inside and the outside of said wound core.

d. A spiral winding for electrical inductive apparatus,

- said spiral winding including a sheet conductor which produces heat when energized, electrical insulation located adjacent to at least one side of said sheet conductor, cooling ducts passing through said winding, said cooling ducts being formed by the staggered juxtaposition of a plurality of holes through the sheet conductor and a plurality of holes through the electrical insulation, the length of said cooling ducts being greater than the radial thickness of the spiral winding to increase the average creepage distance through said ducts.

5. A sheet wound winding for fluid cooled transformers, said sheet wound winding comprising `a plurality of turns separated by electrical insulation, said turns and said electrical insulation each having a plurality of holes positioned in staggered juxtaposed groups to form a plurality of cooling ducts through said transformer winding, said cooling ducts having a length greater than the distance between the inside and outside surfaces ot the sheet wound winding to increase the average creepage distance through said cooling ducts.

6. Cooling means for a heat producing hollow wound structure, said cooling means comprising a central tube located inside of said hollow Wound structure to direct coolant flow, said central tube having an outside diameter less than the inside diameter of said hollow wound structure, said hollow wound structure including a plurality of turns having at least one hole each therein, said g turns being so arranged that cooling ducts are formed between the inside of said hollow wound structure and the outside of said hollow wound structure by the staggered juxtaposition of the holes in said turns, said cooling ducts having a length greater than the radial distance between the inside and the outside of the hollow wound structure.

7. A sheet wound coil for electrical .inductive apparatus, said coil comprising a plurality of turns of an insulated electrical conductor, said conductor being wound about a tube, said conductor having a plurality of holes therein so spaced that groups of holes are placed in staggered juxtaposition to form zig-zag ducts, said zig-zag ducts extending from the outside of the coil to the outside of the tube and back to the outside of the coil.

FOREIGN PATENTS 8,997 1908 Great Britain.

5 LARAMIE E. ASKIN, Primary Examiner.

JOHN P. WILDMAN, Examiner. 

1. A WINDING FOR ELECTRIC INDUCTIVE APPARATUS, INCLUDING AT LEAST ONE SHEET CONDUCTOR HAVING ELECTRICAL INSULATION ADJACENT TO AT LEAST ONE SIDE OF SAID SHEET CONDUCTOR, SAID SHEET CONDUCTOR HAVING A PLURALITY OF HOLES SO SPACED THAT WHEN SAID SHEET CONDUCTOR IS WOUND INTO A COIL THE HOLES IN SAID SHEET CONDUCTOR ARE PLACED IN STAGGERED JUXTAPOISITON TO FORM AT LEAST ONE DUCT THROUGH SAID WINDING. 